View attachment 1449542
In nature they do the same, a male will acquire a territory (like the cave on the right above) in Cenote Cristallino
and the females approach when ready to spawn (like the one on the left) and if they are compatible, he allows her in.
The male above was about 10 tp 12", and you could probably fit a 250 gal in that crevice.
Once together he chases all other males and females away.
You can see below (by the jaw fungus) he had been in many mouth locking battles for dominance, and to hold that coveted, protective spot.
View attachment 1449544
Below a video of a few in a different Cenote.
027 zps4b102ffd
and another
Eden2
View attachment 1449543